Thermo-responsive detecting apparatus



Aug. 1, 1961 c. F. GREEN 2,994,772'

THERMO-RESPONSIVE DETECTING APPARATUS Filed NOV. 29, 1959 AMPLIFIER,

Patented Aug. l, 1961 2,994,772 THERMO-RESPNSIVE DETECTING APPARATUS Charles F. Green, Schenectady, NX., assigner, by mesne assignments, to the United States of America as represented by the Secretary of War Filed Nov. 29, 1939, Ser. No. 306,754 11 Claims. (Cl. Z50-33.3)

This invention, which relates to apparatus for detecting objects by means of the radiation received and particularly to apparatus by which invisible objects such as airplanes may be detected by their heat radiation, is a further development of the apparatus described and claimed in my copending application Serial No. 306,753, filed November 29, 1939, and the copending application of Laurens A. Taylor, Serial No. 306,755, led November 29, 1939, for Detector Apparatus.

One object of this invention is to provide an improved apparatus of the character specified by means of which the orientation of the radiating body in both azimuth and elevation may be accurately determined and easily followed in a program of systematic searching.

Another object of this invention is to provide a detecting vapparatus including a double line thermo-couple vacuum tube arranged within the focal region of a reflector system which will enable effective searching for a fast moving unseen target using a rapidly oscillating beam for spotting purposes.

Another object of this invention is to provide a detecting apparatus including a double line thermo-couple vacuum tube arranged within the focal region of the reflector system, which will afford a pick-up angle having a vertical spread of approximately 3 whereby a plane flying horizontally at a given altitude will require several seconds to fly through the beam.

Another object of this invention is to provide a detecting apparatus including a high vacuum thermo-couple tube containing two line thermo-couple units arranged one above the other, the units being arranged to automatically compensate for changes in background radiation and to give indications that the center of the beam is on the target.

Another object of this invention is to provide a double line thermo-couple vacuum tube wherein the two compensated units are arranged one above the other, the output of each unit being connected to a separate arnplifier-indicator-system, each of which is adapted to be used by an operator during the scanning of each of the apparatus.

With these and other objects in view this invention consists in certain novel details of construction, combination and arrangement of parts to be more particularly hereinafter set forth and claimed. v

Referring more particularly to the accompanying drawings in which corresponding parts are indicated by similar reference characters:

FIG. l is a sectionized diagrammatic view of a collector-thermocoupleamplifier-indicator apparatus, illustrating one embodiment of the instant invention;

FIG. 2 is a sectionized perspective view of a thermoresponsive device adapted to be used in connection with the apparatus shown Vin FIG. l, and illustrating the arrangement, mounting and connections of the thermo- Couple strips within the tube; and

FIG. 3 tis a diagrammatic view of the thermo-line units' and their electrical connections with the terminal block.

In the form of thermo-couple Vacuum tube described and claimed in my copending application filed November 2.9, 1939, Serial No. 306,753, the thermo-couple strips are mounted side-by-side and connected in such a manner that their outputs are in bucking relation. This tube while useful for certain purposes has not proved satisfactory for detecting a fast moving body such as an airplane in flight, and this defect led to the development of the line thermo-couple vacuum tube described and claimed in the pending application of Laurens A. Taylor, iiled November 2.9, 1939, Serial No. 306,755, which afforded a greater vertical acceptance angle and permitted faster searching.

'Ihe pick-up angle of the line thermo-couple tube while constituting quite an improvement over the flrst mentioned tube, was not satisfactory from the standpoint of angle of vertical spread and rapidity of response and for this reason the double line thermo-couple tube forming the subject matter of the instant application was developed. This tube not only provides a vertical acceptance angle of approximately 3 but likewise enables the operators of the detecting apparatus to determine the location of the target.

In the illustrated embodiment characterizing this invention a drum 1 is pivotally mounted at Z between the arms of a yoke 3 which is swivally supported on base 4. This arrangement permits vertical and horizontal oscillation of the drum, as clearly shown in FIG. l of the drawings. Suitable means are provided for moving the drum in each of the two planes whereby changes in elevation and azimuth may be affected for the purpose of pointing the drum. While such means may be manually or power operated, the former is illustrated for the sake of simplicity. Thus the hand wheel 5 operates through worm 6 and wormwheel 7 to move the drum in the vertical plane and the handwheel 8 functioning through worm 9 and wormwheel 10, serves to move the drum in the horizontal plane.

Within the drum is mounted a reflector 12 in the focal region of which is arranged a double line thermo-couple vacuum tube 13, the tube being suitably supported on the upper end of a standard 14, as shown in FIG. 1 of the drawings. This double line thermo-couple tube 13 embodies two line units a and b arranged in superimposed relation, each unit being composed of a pair of thermo-couple strips 1516 and 15a-16a the respective strips of each unit being horizontally disposed and arranged in end to end relation with the junction lines Ztl- 20a and 20h-20c, extending vertically, as clearly shown in FIG. 2 of the drawings.

These line units are mounted within and near one end of an evacuated envelope 17, which comprises a glass portion 18 having a metallic end portion 19 which inthe present instance is in the form of a silver sleeve. The end portion 19 is attached at its free end to 4a window or end plate 21 having a high transmission coeicient for low temperature radiation, such as rock salt. The sleeve has a thin tapered edge at both ends, the glass being fused over the inner end and the outer end of the sleeve is made vacuum tight with the rock salt window by a suitable seal 3 November 29, 1939, Serial No. 306,750, now U.S. Patent No. 2,543,369.

Each of the thermo-couple strips -16 and 15a-16a forming the respective line units a and b has been made by welding together at their edges, thin plates of electrically dissimilar metals and then rolling down the welded plates until they have obtained the desired thinness, which is of the order of 6 to 10 millionths of an inch. Since the direction of the rolling is transversely of the strip, or in other words in the direction of their junction lines, the welded connection between the two metals is preserved even though the thickness of the resulting strip is reduced to a few millionths of an inch. Very successful results have been obtained by employing for one element of the thermo-couple strips 15 and 16 an alloy composed of nickel 44%, copper 35.5% and iron 0.5%, commonly known as Copnic, and for the other element of the thermo-couple strips 15 and 16y an alloy composed of nickel 90% and chromium 10%, commonly known as ChromeL The thermo-couple strips 15 andr16 of the respective units a and b, as previously stated are arranged horizontally in an end to end relation with the junction lines extending vertically.

The two thermo-couple strips 15-16 and 15a-16a of the respective line units a and b are connected in series and in a reverse manner, that is to say the two outer elements 15b-1Gb and 15c--16c of the respective line units a and b which are of one polarity are attached to supporting bars -26 and 25a-26a respectively, and the inner or intermediate elements 15d-16d and 15e-16e of the respective line units which are of the opposite polarity are secured to the intermediate bars 23 and 23a respectively.

The lengths of the electrically dissimilar metals forming each of the thermo-couple strips, are substantially equal, the exact lengths being such that the rates of heat conduction of the supporting bars, considering the heat conducting properties of the materials, are equal. The intermediate bars 2S-23a are approximately twice the size of the outer bars 25-26, 25a-26a, whereby they have approximately twice the heat capacity thereof. Each of the vertically extending junction lines 20-20-20b- 20c is arranged substantially in the middle of its thermocouple strip, as clearly shown in FIG. 2 of the drawings.

In order to bring the junction lines 20-20a-20b- 20c of the respective line units a and b closer together, the inner elements 15d- 16d and 15e- 16e are bent backward, as shown in FIG. 2 of the drawings. By thus bringing the two junction lines 20-20a--20b-20c of the res'pective units a and b closer together, are thermo-couple strip of each unit can be made to respond to a background region of radiation, which is closer to the body, whose radiation elfects the joining strip of said unit, consequently in so far as background radiation is concerned the output of the thermo-couple strips of the respective units will exactly balance one another.

Assuming that the super-imposed thermo-couple strips 15-15a are those to be used for detection of a radiating body, while the other junction strips 16-16a are those to be used for background compensation, then as shown in FIG. 2 of the drawings, the inner bars 2.3-- 2-3a are connected to the conductors 23b-23c, which extend through the stem of the glass envelope 17 to termina-ls 23e23d of terminal block A. The outer bars 25--26 of line unit a are vconnected to conductors 25c- 26c which extend through the tube of envelope 17 to terminals 25d-26d of terminal block A. The remaining bars 25a-26a of line unit b are connected to conductors 25a-26e which extend, as in the case of the other conduct-ors, through the envelope 17 to terminals ZSf-Zf of terminal block A.

Terminals 25d-46d are connected via conductors 25g-26g to the input side of amplifier 31, the output side of which is connected through suitable conductors to a milliammeter indicator 30. The terminals 25f-26f of terminal block A are connected via conductors 25h- 26h to the input side of amplifier 31a, the output side of which is connected to a milliammeter indicator 30a, as clearly shown in FIG. 2 of the drawings.

To correct for small differences in resistance in thermocouple construction, which may occur in manufacture due to the variations in materials, thickness of strips and etc., suitable balancing networks (not shown) may be connected via conductors 35a-35b and 35e-35d between the terminals 23e-26d and 23d-25f respectively, on terminal block A, as clearly shown in FIG. 2 of the drawings. These resistance elements are introduced to balance the output of the respective line units as the beam of the detector is swung from horizon to zenith in a clear sky, and to thus stabilize the pointers of the indicators, as will be understood without'further discussion.

With the components of the instant detecting apparatus arranged as previously stated, its operation is as follows: Assuming that the drum 1 is swung in azimuth, during a search for a radiating body, and that indicator 30 shows a deflection indicating that the image of such body has fallen on the thermo-couple strip 15 of line unit a and has reached junction line 20 of this strip. When this occurs the operator will know that the drum is directed on the meridian containing the radiating body and likewise that the image has fallen on the upper thermocouple strip 15 rather than on the lower thermo-couple strip 15a. In order that the operator may determine the exact position of the body in elevation, as well as in azimuth, drum 1 is tilted by manipulation of handwheel 5 to cause the image of the radiating body to move downwardly along junction line 20 of unit a.

When the drum 1 has been changed in elevation sufficiently, the image of the body will reach the focal point 42 where it will begin to leave the upper line unit a and enter upon the lower line unit b. The deflection of the indicator 30 will thereby decrease while the deilection of the instrument 30a will increase. By careful manipulation of the elevating control handwheel 5 and if the object is moving in azimuth, by simultaneous manipulation of the handwheel 8 in a suitable manner, the image of the radiating body can be retained exactly on the focal point 42 in which case both indicators 30 and 30a will show approximately equal deflection. The drum under these conditions is pointed directly at the radiating body, whereupon the position of the body in azimuth and elevation may be read from the scales, not shown, with which the drum 1 is provided. Obviously, if the image of the body is rst picked up by the lower line unit b the elevation of the drum will be changed in the opposite manner until the image reaches the focal point 42, where it will be held as previously stated.

In conclusion it will seem this invention provides a detection apparatus which not only gives a vertical angle of acceptance greater than that afforded by the detection apparatus described and claimed in the two applications hereinabove referred to, but likewise enables the operator to determine the exact position of the radiating body in azimuth and in elevation.

Having described my invention, what I claim as new and wish to secure by Letters Patent is:

l. In an apparatus for locating distant bodies by thermo-radiation, means for collecting and focusing the heat radiation from a distant body, means within the focal region of collected radiation for translating thermal into electrical energy, said means including means for detecting the position of heat radiating body in azimuth and in elevation, and comprising an evacuated vessel provided with a rock-salt Window, a pair of thermo-electric generating units arranged within the vessel one above the other, each unit being composed of a pair of thremo- 'couple strips disposed in end to end relation and electrically connected in opposition to `afford automatic compensation for changes in background radiation, each of said strips being formed withvertically extending junction lines, the junction lines of one of said units being in alinement with those of the other of said units, and a separate indicator system in an electrical relation with each of said units.

2. In an apparatus for locating distant bodies by thermo-radiation, means for collecting and focusing the heat radiation from a distant body, means within the focal region of the collected radiation for translating thermal into electrical energy, said means including means for detecting the position of the heat radiating body in azimuth and in elevation, and comprising a highly evacuated vessel provided with a window transparent to thermal radiation, a pair of thermo-electric generating units, each of said units including a pair of thermo-couple strips arranged in end to end relation, the strips of the respective units being electrically connected in opposition to afford automatic compensation for changes in background radiation, each of said strips being formed with vertically extending junction lines, the junction lines of one of said uni-ts being alined with those of the other of said units, and a separate indicator system in electrical relation with the output of said units.

3. In an apparatus for locating distant bodies by thermo-radiation, means for collecting and focusing the heat radiation from a distant body, means within the focal region of collected radiation for translating thermal into electrical energy, said means including means for detecting the position of the heat radiating body in azimuth and in elevation, and comprising an evacuated vessel provided with a rock-salt window, thermo-responsive means within the vessel immediately to the rear of said window, said means including a pair of thermo-electric generating units situated one above the other, each unit consisting of a pair of thermo-couple strips electrically connected in opposition to aiord automatic compensation for changes in background radiation, the width of said strips being such as to afford a wideyvertical acceptance angle, each strip having a vertically'disposed junction line coextensive with the Width of the strip, the junction lines of the upper unit being in alined and spaced relation With respect tothe underlying unit, andl a separate indicator system in electrical relation with the output of each of said units.

4. In an apparatus for locating distant bodies by thermo-radiation, means for collecting and focusing the heat radiation from a distant body, means Within the focal region of the collected radiation for translating thermal into electrical energy, said means including means for detecting the position of the heat radiating body in azimuth and in elevation, and comprising an evacuated vessel provided with a rock-salt window, a pair of thermoelectric generating units situated within the vessel immediately to the rear of said Window, each of said units including a pair of thermo-couple strips arranged in end to end relation and electrically connected in opposition to provide a bucking output, each of said thermo-couple strips having a vertically extending junction line coextensive with its width, the junction lines of one of said units being in alinement with those of the other of said units, and each thermo-couple strip being bent rearwardly to position the junction lines of adjoining strips a predetermined distance apart and a separate indicator system in electrical relation with the output of each of said units.

5. In an apparatus for locating distant bodies by thermo-radiation, a reflector system for collecting and focusing heat radiation from a distant body7 means within the focal region of the reector system for translating thermal into electrical energy, said means including means for detecting the position of the heat radiating body in azimuth and in elevation land comprising an evacuated vessel provided with a rock-salt Window, a pair of thermoelectric generating units situated one above the other Within the vessel and immediately to the rear of said window, each unit being composed of a pair of thermocouple strips arranged end to end and interconnected at' their inner extremities in bucking relation, each strip having a junction line coextensive with its width, the junction lines of one unit being in aligned relation with respect to those of the underlying unit, one pair of aligned junction lines being disposed so that the focal point of the reflector system will be located between the units and at the meeting ends of said aligned junction lines and a separate indicator system in electrical relation with the output of each of said units,

6. In an apparatus for locating distant bodies by thermo-radiation, a reector system for collecting and focusing heat radiation from a distant body, means within the focal region of the reiector system for translating thermal into electrical energy, said means including means for detecting the position of the heat radiating body in azimuth `and in elevation and comprising an evacuated Vessel provided with a window transparent to thermal radiation, a pair of thermo-electric generating units situated one above the other within the vessel and immediately to the rear of said Window, each unit being composed of a pair of thermo-couple strips situated end to end and interconnected at their inner extremities in bucking relation, each thermo-couple strip having a junction line coextensive with its width, the junction lines of one unit being in aligned relation with respect to those of the underlying unit, one pair of aligned junction lines being `disposed so that the focal point of the reflector system will be located between the units and at the meeting ends of said aligned junction lines and a separate indicator system in electrical relation with the output of said units.

7. A thermo-responsive device comprising an evacuated envelope provided with a window transparent to thermal radiation, a pair of thermo-electric generating units within the envelope immediately to the rear of said window, said units being situated one above the other and each unit being composed of a pair of thermo-couple strips arranged end to end and connected in bucking relation, each thermo-couple strip having a vertically disposed junction line coextensive with its Width, the junction lines of one of said units being in alined relation with those of the other of said units.

8. A thermo-responsive device comprising an evacuated envelope provided with a window transparent to thermal radiation, a pair of thermo-electric generating units within the envelope immediately to the rear of said window, said units being situated one above the other and each unit being composed of a pair of thermo-couple strips arranged end to end `and connected in bucking relation, each thermo-couple strip embodying electrically dissimilar elements united along a vertically extending junction line coextensive with the width of the strip, the junction lines of one of said units being in alined relation with those of the other of said units and having a predetermined spacing.

9. A thermo-responsive device comprising an evacuated envelope provided With a rock-salt Window, a pair of thermo-electric generating units within the envelope immediately to the rear of said window, said units being situated one above the other and each unit being composed of a pair of thermo-couple strips arranged end to end and connected in bucking relation, said thermocouple strips embodying electrically dissimilar inner and outer elements, united lalong a vertically disposed junction line coextensive with the width of the strip, the inner elements of the adjoining strips being bent backwards to provide a predetermined spacing for the junction lines of each unit and the outer element-s of the upper and lower thermo-couple strips being disposed to position said thermal junction lines in alined relation.

l0. A thermo-responsive device comprising an evacuated envelope provided with \a window transparent to thermal radiation, a pair of thermo-electric generating units within the envelope immediately to the rear of said Window, said units being situated en@ aber@ the other and each unit being composed of a pair of thermo-couple strips of a predetermined order to thinness and arranged in end-to-end relation and connected in electrical opposition within said envelope, each thermo-couple strip having a vertically-disposed junction line coextensive with its width, the junction lines of one of said units being in aligned relation with those of the other of said units.

1l. A thermo-responsive device comprising an evacuated envelope provided with a window transparent to thermal radiation, a pair of thermwelectric generating units within the envelope immediately to the rear of said window, said units being situated one above the other and each unit being composed of a pair of thermo-couple strips 6` to 10 millionths of an inch in thickness and ar- References Cited in the le of this patent UNITED STATES PATENTS 1,343,393 Hoffman June l5, 1920 1,963,185 Wilson June 19, 1934 2,125,113 Kling July 26, 1938 2,144,519 Wilson Jan. 17, 1939 

